RENE RAMOS DE OLIVEIRA

RENE RAMOS DE OLIVEIRA

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Effectiveness of modified lignin on poly(butylene adipateco-terephthalate)/poly(lactic acid) mulch film performance
2023 - BARROS, JANETTY J.P.; OLIVEIRA, RENE R.; LUNA, CARLOS B.B.; WELLEN, RENATE M.R.; MOURA, ESPERIDIANA A.B.
In this work, the biodegradable poly(butylene adipate-co-terephthalate) (PBAT)/ poly(lactic acid) (PLA) blend (ECOVIO®) and lignin, a renewable and biodegradable natural polymer with high UV absorption and modified by gamma radiation were used to produce agriculture mulch films. Lignin was gammairradiated at 30 and 60 kGy. The irradiated and non-irradiated lignin content of 2 wt% was incorporated into PBAT/PLA blend matrix using a twin-screw extruder and extrusion blown film to prepare flexible films. PBAT/PLA/LIGNIN films were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), tensile tests, contact angle, and UV–Vis analysis. FTIR spectra showed partial miscibility between PBAT/PLA and lignin, being intensified in irradiated lignin compounds. The DSC and XRD results confirmed that the degree of crystallinity of the blends was not significantly influenced by lignin addition. FE-SEM images showed better dispersion and miscibility in PBAT/PLA/Irradiated lignin. Miscibility improvement provided by irradiated lignin promoted better mechanical properties, mainly with lignin irradiated at 60 kGy. PBAT/PLA/LIGNIN films containing 2 wt% showed excellent UV-barrier property and greater hydrophobicity. Summing up, incorporation of low contents of irradiated lignin could be an interesting alternative to produce biodegradable UV-blocking agriculture mulch films.
Synergistic effect of polylactic acid(PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blend and cellulose nanowhiskers for sustainable packaging applications
2020 - MOURA, E.A.; SANTOS, B.S.; OLIVEIRA, R.R.; RODRIGUES, R.C.
Conventional food packaging is in general, not recyclable, based on practically undegradable petroleum-derived polymers, and consequently not selectively collected. Concerns over their environmental impact and sustainability issues posed by their production and disposal and trends have increased interest and driven the effort to generate biobased and biodegradable packaging to replace or complement the conventional ones. The aims of this work are to investigate the development of biocomposite films composed of biodegradable polylactic acid(PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blend and cellulose nanowhiskers extracted from agro-waste and evaluate their potential use in sustainable food packaging application. Biocomposite films based on biodegradable PLA/PBAT blend containing 1-2 wt. % of cellulose nanowhiskers extracted from agro-waste were prepared by melt extrusion, using a twin-screw extruder machine and blown extrusion process. To evaluate the potential use in food packaging applications, the cellulose nanowhiskers' content on the morphological, mechanical and thermal properties of the as obtained biocomposite films has been assessed. In addition, cellulose nanowhiskers were characterized by TEM, DLS, XRD, and TG. The results showed that cellulose nanowhiskers addition leads to an important increase in thermal degradation temperature, melting enthalpy and tensile properties of biocomposite films. The increases in the melting enthalpy can be attributed to the increase in the crystallinity of PBAT/PLA biocomposite as a result of cellulose nanowhiskers' addition. Morphology and thermal tests were related to the properties of the films and confirmed that cellulose nanowhiskers were homogeneously dispersed into the matrix. Based on the results, this research demonstrated that the use of biodegradable polymer blend and cellulose nanowhiskers extracted from agro-waste represents an interesting alternative for the production of flexible biocomposite films for sustainable food packaging applications and for the development of eco-friendly technologies.
Effect on flame propagation in recycled expanded polystyrene with flame retardant/white clay/titanium dioxide nanocomposite
2020 - BARTOLOMEI, S.S.; BARTOLOMEI, M.R.; MOURA, E.M.; WIEBECK, H.; OLIVEIRA, R.R.
Polystyrene is widely used in construction due to its properties such as low density, heat resistance, durability and ease of processing and molding. However, it is highly flammable, releases a lot of heat and toxic smoke when exposed to a flame. However, in order for a material to be applied in habitable indoor environments, it must comply with fire safety standards, which predict the behavior of materials during their burning. Halogenated flame retardants have been used to reduce the spread of flame, but they are toxic and polluting, so more environmentally friendly products are being developed. Polymeric nanocomposites, formed by inorganic nanoparticles, have many advantages in flame retardation, such as low heat release rate, low smoke and toxic gas production. Alternatively, the organofilized, exfoliated or polymer-intercalated montmorillonite clay (MMT) can be used to form a nanocomposite with greater flame resistance. However, for the clay to achieve the results required by the standards, it is necessary to add a large amount of particles, which generates agglomerates in the material and losses in the mechanical properties. Therefore, the use of clays to improve flame resistance to the material must be accompanied by the use of other flame retardants. Thus clay will provide reduction in flammability and secondary flame retardant will provide ignition resistance. The addition of other particles, together with clay, can corroborate with the reduction in flame spread of the material, with titanium dioxide being used to increase thermal stability, UV light stability, mechanical properties as well as reduction in flame spread. In this work expanded polystyrene (EPS) from construction waste, with flame retardant in its composition, was recycled and plasticized with glycerol. In this polymeric matrix was added white clay and titanium dioxide in order to maintain the flameproof properties and improve the mechanical and thermal properties of the material. The results showed that it is possible to recycle EPS and maintain flame self-extinguishing through the material even in the presence of glycerol as plasticizer. The addition of white clay improved the mechanical properties of the material and increased thermal stability, but impaired the fire behavior of the material, ceasing to self-extinguish the flame immediately after extinguishing the external flame. Titanium dioxide (TiO2) kept the mechanical and thermal properties unchanged and reduced flame propagation in the specimen when compared to the results of clay nanocomposite.
Graphene oxide nanosheets as fillers for thermoplastic-matrix nanocomposites
2020 - MOURA, E.A.; SANTOS, B.S.; ISHIKAWA, O.; SANTANA, J.G.; BARTOLOMEI, M.R.; OLIVEIRA, R.R.
Recent studies have shown that the synthesis of graphene oxide (GO) by chemical oxidation of graphite followed by its reduction is one's the most promising routes to prepare remarkable polymer/graphene nanocomposite materials with significant improvement of properties compared to the base polymer. The addition of a very small amount of reduced graphene oxide (RGO)in a polymer can enhance its properties, with respect to electrical conductivity, barrier resistance, stiffness, abrasion resistance, mechanical resistance, and fire retardancy. Numerous approaches have been established to prepare RGO from the desoxygenation of GO. This work presents the synthesis of graphene oxide by chemical oxidation of graphite followed by its photoreduction in aqueous dispersion using UV radiation and highlights some examples of RGO/thermoplastic-matrix nanocomposites prepared by melt processing. To evaluate the potential application of thermoplastic composites prepared, the RGO's content on the morphological, mechanical and thermal properties of the as-obtained nanocomposites has been assessed. In addition, GO/RGO nanosheets were characterized by ATR–FTIR, XRD, Raman, and FE-SEM. According to the results, it can be inferred that the addition of RGO leads to a remarkable improvement in the performance of thermoplastic-matrix nanocomposites and offers a competitive solution for various potential applications.
Sonochemical synthesis of reduced graphene oxide
2020 - MOURA, E.A.; ISHIKAWA, O.; MANGIERI, F.; BARTOLOMEI, M.R.; BARTOLOMEI, S.S.; OLIVEIRA, R.R.; FRANCISCO, D.L.; GUIMARÃES, K.
The reduction of graphene oxide (GO) by a safe and eco-friendly route, without the use of harmful chemicals, has drawn much attention as one of the most promising routes to produce graphene nanosheets, a 2D material with excellent electrical and thermal conductivity, optical and mechanical properties. Graphite exfoliation is widely performed by the chemical reduction of GO, which is commonly produced by oxidation of graphite using a strong oxidizing agent by Hummers’ method. This work presents a study of the influence of sonochemical application on synthesis of reduced graphene oxide induced by UV radiation. Commercial graphite powder was used as raw material. Firstly, graphite powder was dispersed into a DMF/deionized water solution and ultrasonicated using a high intensity ultrasonic device for 1 8 hours in other to reduce the particle sizes. After, sonicated graphite samples were frozen for 24 hours and freeze-dried for 24 hours to obtain the powder. Graphite powder obtained with different particle sizes was used to prepared GO through a chemical route. GO prepared was dispersed into a DMF/deionized water solution, ultrasonicated using a high intensity ultrasonic device for 1-2 hours, frozen for 24 hours and freeze-dried for 24 hours. Finally, GO powder samples were dispersed in a mixture of isopropyl alcohol, acetone, and deionized water and irradiated using UV radiation by different irradiation time to obtain reduced GO (RGO). The GO and RGO were characterized by BET, ATR–FTIR, XRD, Raman, TG, and FE-SEM analysis. In addition, graphite samples were characterized by BET, SEM and XRD analysis. The results showed that sonochemical application has a fundamental role in the synthesis of GO nanosheets and RGO. Ultrasonically prepared GO exhibited higher surface area, higher crystallinity and higher oxidation efficiency with many hydrophilic groups. FE-SEM analysis of the GO showed that sonochemical application reduced the aggregated domains and close stacking of sheets on the GO surface and led to obtaining reduced GO with a smooth surface, fewer layers and significant effective surface area.
Production and characterization of PBAT reinforced with clay and graphene oxide nanosheets
2020 - COSTA, ROBSON S.; ARAUJO, DANIELLE G.; ANDRADE, MARCIO S. de; OLIVEIRA, RENE R.; RANGARI, VIJAYA; MOURA, ESPERIDIANA A.B.; DIAS, FRANCISCO V.
The poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polymer, is among the most promising materials to be considered as environmentally friendly high performance biodegradable plastics. However, the mechanical properties of PBAT are not the best for several applications. According to the literature, the properties of the biodegradable polymer can be improved by addition of a small amount of nanofillers, such as clay, silica, and graphene. The objective of this study is to compare the effect of the addition of Cloisite clay and graphene oxide (GO) on the properties of flexible films based on PBAT matrix. The composite films based on PBAT with addition of Cloisite (2.0 wt%) and PBAT composite films with addition of Cloisite and GO (0.1–0.2 wt%) were prepared by extrusion, using a twin-screw extruder and a flat die single extruder. The effects of the addition of Cloisite clay and graphene oxide on mechanical and thermal properties of films were evaluated by mechanical and water absorption tests, FE-SEM, XRD, and Raman analysis.
Mechanical and morphological properties of hybrid composites based on recycled LDPE/EVA blend reinforced with clay and babassu fiber residues
2020 - TAMURA, CAROLINE S.; ARANTES, MARIANA; CARMO, KARINA H.S.; SANTOS, BIANCA S.; OLIVEIRA, RENE R.; MOURA, ESPERIDIANA A.B.
Over the years the consumption of plastic products made of conventional polymers has produced a large amount of waste which has led to disposal problems worldwide. Among the alternatives to minimize these problems are reuse and recycling practices. Then, the recycling of plastic and the use of recycled materials to produce new materials reinforced with nanoparticles from natural resources can be an alternative to reduce inappropriate waste disposal. The objective of this study is to investigate the effects of the addition of clay and non-treated babassu fiber residues on the mechanical and morphological properties of composite based on recycled LDPE/EVA blend. Composite materials containing 1–3 wt% of babassu residues and 1 wt% of clay were prepared using a twin-screw extruder machine and flat die single extrusion process, in order to prepare hybrid composites sheets. The sheets prepared by recycled LDPE/EVA blend and its composites were characterized by tensile tests, XRD, and FE-SEM analysis and the correlation between properties was discussed.
Investigation on mechanical and thermal behaviours of PBAT/PLA blend reinforced with reduced graphene oxide nanosheets
2020 - BARTOLOMEI, MARCIO R.X.; CARMO, KARINA H.S.; SANTOS, BIANCA S.; BARTOLOMEI, SUELLEN S.; OLIVEIRA, RENE R.; MOURA, ESPERIDIANA A.B.
The aim of this study was to process and investigate the changes in the mechanical and morphological properties of the biodegradable nanocomposites based on polybutylene adipate-co-terephthalate (PBAT)/poly(lactic acid) (PLA) blend (PBAT/PLA blend) due to the incorporation of reduced graphene oxide (RGO) nanosheets. The biodegradable polymeric nanocomposites were prepared by melting extrusion process using a twin-screw extruder machine. The influence of the RGO nanosheets incorporation on mechanical and thermal properties of PBAT/PLA blend was investigated by tensile Thermogravimetric (TG), X-Ray diffraction (XRD), differential scanning calorimetry (DSC), and tensile test analysis. Results showed that incorporation of the small amount ofRGO(0.1wt.%) ofRGOnanosheets in the blend matrix of PBAT/PLA resulted in an important gain of mechanical properties of the blend. This result indicates that a very small amount of RGO nanosheets addition in the PBAT/PLA can lead to obtaining materials with superior properties suitable for several industrial applications.
Influence of the reduced graphene oxide incorporation on properties of acrylonitrile butadiene styrene (ABS)
2020 - SANTOS, BIANCA S.; INACIO, ANDRE L.N.; BARTOLOMEI, SUELLEN S.; SILVA, TAISE B.S.; CARMO, KARINA L.S.; OLIVEIRA, RENE R.; MOURA, ESPERIDIANA A.B.
The purpose of this study was to evaluate the influence of incorporation of the reduced graphene oxide on properties of acrylonitrile butadiene styrene (ABS). The incorporation of 0.5 and 1.5 wt% of RGO into ABS matrix was carried out by melting extrusion process using a twin-screw extruder and injection molding machine. The properties of ABS/RGO nanocomposite samples were investigated by tensile and impact Izod tests, FE-SEM, and XRD analysis. The results showed that the incorporation of small amount of RGO into ABS matrix led to obtaining of polymeric nanocomposite with superior mechanical properties when compared with original properties of ABS matrix.
Improvement properties of polypropylene by graphene oxide incorporation
2020 - TATEI, TATIANE Y.; FONTES, ERIC H.; MOREIRA, RENAN P.; DIAS, FRANCISCO V.; OLIVEIRA, RENE R.; RANGARI, VIJAYA; MOURA, ESPERIDIANA A.B.
Due to the remarkable properties of graphene oxide (GO) and its possibility of functionalization,GOhas been used in many applications such as nanocomposites. GO nanosheets have been shown to improve the properties of the polypropylene (PP) matrix, for instance, its strength, gas barrier, thermal, and electrical conductivity. As PP has relatively low cost and varied applications, this work aims to study the changes in its thermal, morphological, and mechanical properties, due to the incorporation of GO in the PP matrix. GO was synthesized from graphite by a modified Hummers method. The nanocomposites PP/GO with 0.1, 0.2, and 0.3 wt% of GO in the PP matrix were obtained using a twin-screw extruder and an injection molding machine via a melt blending process. The nanocomposites PP/GO were characterized by FE-SEM and Izod impact test. In addition, the GO nanosheets were also characterized by Raman spectroscopy, ATR-FTIR, FE-SEM, and XRD, therewith correlation between properties was discussed.